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Old 5th July 2008, 09:56 PM   #1
daring is offline daring  United States
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Default Yamaha surround receiver questions

Hello all! First time poster here. I'm a big fan of DIY. Currently working on an LCD projector and audio amplifier project. I have a situation that I wanted to get some input on. I have a Yamaha HTR-5930 surround sound receiver that has been damaged on one side rendering it useless for home theater (the digital input board was busted), but most of the PCB's inside the case are OK.

What I want to know is can I salvage a decent stereo amplifier from the components in this thing? I have removed what appears to be the main amplifier board (labeled "FUNC 4"), which has 5 chips in a row that were clipped to a large heatsink. My guess is that these are the individual channel amp chips. There are also a ton of resisters, capacitors, etc.

Am I wasting my time with this thing? I am currently looking into getting a Gainclone or similar project going but I thought it would be nice to have a substitute amp while I was working on the other project. I have a set of amazing AR.Com bookshelf speakers (8 Ohm speakers) that are just sitting here making no sounds...

Any input would be greatly appreciated. Please take it easy on the "newbie" around here.
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Old 5th July 2008, 11:26 PM   #2
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Hi Daring,

Welcome to the club, please be aware that this hobby is very addictive.

There is always a way to salvage at least 2 stereo set from a 5 channels but you'll have to do reverse engineering to find out what connects where. I do not know your background but it could be easy or hard, since the unit is not useful you may as well work at it for fun. I really like the sound of Yamaha so I would give it a try.

Another solution is to salvage the power transformer + bridge rectifier + filtering capacitors (the big one) and to build a set of gainclone.

What ever you choose, have fun.
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Old 6th July 2008, 04:14 AM   #3
daring is offline daring  United States
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Yeah, at this point I figure I might as well try to mess around with it and get something useful out of it. There are two of the five chips that have the same numbers "7805A" on them. I'm guessing they are the two front channels. All the other 3 chips are different.

I guess I should post some pics so those who are interested can give me some advice. Like they say, a picture is worth a thousand words!
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Old 6th July 2008, 11:48 AM   #4
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7805 is a voltage regulator. They are probably there for some auxiliary circuits. Might be volume or tone control, motorized potentiometers, even preamplifier ICs.

The other three chips will be the interesting ones. They are probably two-channel amplifier ICs like LM1876 or LM4780. One channel for each of the five satellites and one channel for the subwoofer would fit. Try to find out their codes for further investigation.
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Old 6th July 2008, 03:45 PM   #5
daring is offline daring  United States
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Well, we are making some progress now. The other 3 chips are labeled as follows: 2388, 7812, 7912PI. There are also 3 large Sanyo chips labeled: STK433-130 (x2), and STK404-130Y. Could these be the main amplifier chips?

Here are a couple pics of the boards.

Click the image to open in full size.

Click the image to open in full size.

Anybody who can help me identify the parts I need to use to make a working stereo amp would be awesome. I figure there is plenty here to use. I also have the big transformer block (BANDO X6311 BO). Thanks!
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Old 6th July 2008, 07:00 PM   #6
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7812 and 7912 are also voltage regulators. 2388 could be one as well, but the letters before the numbers are missing. The STKs are your amplifiers.
STK404-130 is a 1x100W type. The datasheet is available on http://www.datasheetcatalog.net/. Look for the type with the S at the end. The other one is in Japanese.
STK433 seems to be the stereo version of it, although I didn't find a datsheet. The outer components will be very similar however.
Yamaha claims 5x110 W, so that seems to fit as well.

Did you check the fuses? Maybe all you have to dois disconnect the broken input board to make sure there are no shorts, and then the amp section and analog inputs works again.
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Old 6th July 2008, 08:28 PM   #7
daring is offline daring  United States
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Great! Thanks for the help. I was gentle before about the condition of this receiver. It is almost completely dismantled so working as it once did it out of the question.

I tried to insert some pictures of it in my last post but they didn't seem to come through. Maybe this will work:

http://www.flickr.com/photos/daring72/2642429672/

Looks like I've found my amp chips anyway. Now I need to round up the other components that will be needed. What is a good place to get simple PCB's, like for projects?
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